The primary aim of the proposed research is to determine the validity of BK5.erbB2 transgenic mice as a model for testing novel therapeutic strategies for biliary tract cancer. Recently, we developed the BK5.erbB2 transgenic mice where expression of rat erbB2 in the biliary tract epithelium leads to development of papillary adenocarcinoma of the gallbladder. Current chemotherapeutic strategies for treating human biliary tract cancers include nucleoside analogs such as 5-FU and gemcitabine although with limited success. Because BK5.erbB2 mice represent the first genetically engineered mouse (GEM) model for biliary tract cancer, they have the potential to provide a novel model for preclinical screening of both traditional and novel treatment strategies for this devastating human cancer. In BKS.erbB2 mice, we have found that the EGFR, COX-2 and c-Met protein levels are elevated in gallbladder adenocarcinomas. Similar changes have been observed in human biliary tract cancers. We aim to improve the selectivity of current therapy and identify novel therapies by targeting the specific genes that are overexpressed in gallbladder cancer. The following two strategies will be used to target overexpressed genes in biliary tract cancers: chemical inhibitors of EGFR and COX-2 at the protein level and triplex forming oligonucleotides (TFOs) to inhibit transcription of EGFR, COX-2 and c-Met genes at the DNA level. Both of these strategies will be tested alone and in combination with nucleoside analogs currently being used in the clinic to treat human biliary tract cancers. TFOs can "also be used to specifically induce unscheduled DNA repair synthesis in tumor cells which overexpress these genes, thereby increasing incorporation of clinically used antimetabolites. Our hypothesis is that inhibition of specific genes either at the DNA or protein level and/or induction of DNA repair synthesis in conjunction with standard antimetabolite therapies will produce a synergistic therapeutic effect in the treatment of biliary cancers in BK5.erbB2 mice. The Specific Aims are: 1) To examine the therapeutic efficacy of 5-FU and gemcitabine as single agents and in combination with each other toward gallbladder cancer in BK5.erbB2 transgenic mice; 2) To determine the therapeutic efficacy of selective EGFR and COX-2 inhibitors at the protein level alone or in combination with each other and in combination with gemcitabine toward gallbladder cancer in BK5.erbB2 transgenic mice; and 3) To measure the effects of TFOs targeted to EGFR, COX-2, and c-Met on gene expression, unscheduled DNA repair synthesis, and tumor growth properties alone or in combination with gemcitabine in gallbladder BK5.erbB2 mice.